Nanoliposomes are important carriers capable of packaging drugs for various delivery applications. Rhenium-188-radiolabeled
liposome ((188)Re-liposome) has potential for
radiotherapy and diagnostic imaging. To evaluate the targeting of (188)Re-liposome, biodistribution, microSPECT/CT, whole-body autoradiography (WBAR), and pharmacokinetics were performed in LS-174T human
tumor-bearing mice. The comparative therapeutic efficacy of (188)Re-liposome and
5-fluorouracil (5-FU) was assessed according to inhibition of
tumor growth and the survival ratio. The highest uptake of (188)Re-liposome in LS-174T
tumor was found at 24 hours by biodistribution and microSPECT/CT imaging, showing a positive correlation for
tumor targeting of (188)Re-liposome using the Pearson's correlation analysis (r=0.997). Pharmacokinetics of (188)Re-liposome showed the properties of high circulation time and high bioavailability (mean residence time [MRT]=18.8 hours, area under the curve [AUC]=1371%ID/g·h). For therapeutic efficacy, the
tumor-bearing mice treated with (188)Re-liposome (80% maximum tolerated dose [MTD], 23.7 MBq) showed better
tumor growth inhibition and longer survival time than those treated with
5-FU (80% MTD, 144 mg/kg). The median survival time for mice treated with (188)Re-liposome (58.5 days; p<0.05) was significantly better than those of
5-FU (48.25 days; p>0.05) and
normal saline-treated mice (43.63 days). Dosimetry study revealed that the (188)Re-liposome did not lead to high absorbed doses in normal tissue, but did in small
tumors. These results of imaging and biodistribution indicated the highly specific accumulation of
tumor after intravenous (i.v.) injection of (188)Re-liposome. The therapeutic efficacy of radiotherapeutics of (188)Re-liposome have been confirmed in a LS-174T solid
tumor animal model, which points to the potential benefit and promise of passive nanoliposome delivered radiotherapeutics for
cancer treatment.